1. Field of the Invention
The present invention relates to cross-connect terminals and more particularly to a pole mounted terminal in which the terminal blocks used therein are arranged in a manner so as to facilitate and encourage minimal jumper routing between blocks and also in which the cables enter the terminal in a manner so as to make dressing of the cables to either side of the pole easy and convenient.
2. Description of the Prior Art
Under certain circumstances, it may be desirable for the telephone operating company to mount a cross-connect terminal, contained in a suitable enclosure, on a pole. The terminal provides the point of interconnection between the multi-pair cable connected to the central office (C.O.) and the cable pairs connected to the local subscribers. It is also desirable that such pole mounted terminals provide for the interconnection of a large number of subscribers to the central office.
The terminal is made up of a multiplicity of terminal blocks. These blocks are arranged in two distinct groups or fields. One such group is the feeder field to which the pairs contained in the C.O. cable are connected. The other such group is the distribution field to which the subscriber cable pairs are connected. The C.O. and subscriber cable pairs are connected to the rear face of the blocks making up their respective fields.
Each block includes on its front face a multiplicity of connection points. There are two such points for each cable pair connected to the rear of the block. Jumper wires are then used to interconnect the appropriate connection points of the feeder field to the appropriate connection points of the distribution field. These jumpers allow the subscriber cable pairs to be connected to the C.O. The number of connection points in the feeder field must be at least equal to the number of connection points in the distribution field in order for a subscriber cable pair to have its own uniquely associated C.O. cable pair.
It has been recognized that it is necessary to have more connection points in the distribution field than in the feeder field. This allows some of the subscribers to have a second cable pair at their location. Over the years, the ratio of feeder connection points to distribution connection points has increased from 1:1 to 1:1.2 to 1:1.5.
With the recent introduction of the Serving Area Concept in the telephone industry, it is now preferred that the ratio be 1:2. Therefore, a cross-connect terminal embodied in accordance with the above ratio will have twice as many distribution connection points as feeder connection points. As is typically the case, identical terminal blocks are used to embody both fields. Thus the cross-connect terminal must have twice as many distribution terminals blocks as feeder terminal blocks.
The dimensions of the terminal will depend upon the total number of connection points (pairs) contained therein and the type of cross-connect block used for the feeder and distribution fields. In general, cross-connect blocks typically provide connection points for either 25 or 50 cable pairs. One such block, which provides connection points for 25 cable pairs, is the BT Series block manufactured by Assignee's Reliable Electric Division in Franklin Park, Ill. A block which provides connection points for 50 cable pairs is the quiet front type of block also manufactured by Reliable Electric. Cross-connect terminals having the ratio of 1:2 and providing connection points for a large number of pairs, such as 1800, have been manufactured using either of the block types described above.
As will be described in more detail hereinafter, those blocks are usually arranged in pad mounted terminals such that the enclosures used to house those terminals are relatively low in height but are long in length. Those dimensions give rise to a terminal, which has been found to be less intrusive to the surroundings, where such terminals are typically placed.
Pole mounted terminals present different requirements. The typical telephone pole is about 12" (about 304 mm) in diameter although the diameters of the poles may range from 8" (about 203 mm) to 16" (about 406 mm). It is, therefore, desirable that the terminal enclosure be of a width such that when mounted on the pole it does not extend appreciably beyond the pole. The narrower in width that the enclosure can be made, the more stability it will have when mounted on the pole and the easier it will be for a craftsperson to climb around it when scaling the pole.
Pole mounted cross-connect terminals have been constructed using conventional arrangements of terminal blocks. As the number of total pairs to be provided by those terminals increases above a predetermined number, such as 1000, the dimensions of the terminal becomes such that the enclosure's horizontal extent is substantially beyond each edge of the pole. When that extent is combined with the height of the enclosure required to have such a large number of pairs, the portion of the enclosure extending beyond the pole becomes a large surface area. This large surface area may then be subject to a large wind generated force and the enclosure may become unstable. In addition, the large overhanging surface area may also present an obstacle to traffic and/or pedestrians as well as become a substantial obstacle to a craftsperson attempting to climb the pole.
In addition, the enclosure may be required to be mounted on the pole either such that its entire interior is easily accessible by a craftsperson standing on the ground or at such an elevation that the craftsperson must use a lift bucket in order to access the interior. In either case, it is desirable that the length of the enclosure be more than about 5' (1524 mm). This length allows all of the terminal blocks contained therein to be easily accessed by a craftsperson, no matter where that person is standing.
For the reasons discussed, it is clear that it is not feasible to pole mount conventionally arranged terminals designed solely for pad mounting. In addition, it is also clear that even conventionally arranged terminals designed for pole mounting give rise to problems where they have to have the capacity to serve a large number of total pairs. Therefore, when the desire to have the 1:2 ratio described above is combined with the desire of the telephone company to serve as many subscribers as possible from a pole mounted cross-connect terminal, it became clear that the conventional arrangement of the blocks currently in use would not be suitable for a cross-connect terminal which has the desired characteristics of being easily and stably mounted to the pole, not an obstacle when so mounted and has its entire interior easily accessible.
In the past, it has been common for the cables to enter a pole mounted terminal either through the top or bottom of the enclosure depending on whether the cable is above or below the ground. The cable travels either down or up the pole and must then be bent away from the pole in order to enter the top or bottom of the enclosure, respectively. As the number of subscribers to be served by a pole mounted terminal increases, the number of pairs contained in the cable and its diameter both increase. This increase in cable size makes it increasingly difficult to easily bend the cable away from the pole so that it can enter the top or bottom of the enclosure. This difficulty in bending large cables also make it hard to obtain a good seal at the point at which the cable enters the enclosure. Lack of such a good seal may allow moisture to enter the enclosure. It therefore became clear that enclosures having top or bottom entry for cables would not be suitable for pole mounted terminals designed to serve a large number of subscribers.